The devil is not as black as he's painted
No one is as bad as people say he is.
From: TFD Idioms
It can also be used to refer to things or situations:
The proverb the devil is not as black as he is painted, first recorded in English in the mid 16th century, was used as a warning not to base your fears of something on exaggerated reports.
Oxford Dictionary of English Idioms by John Ayto
This is a proverb and as StoneyB said in his comments didn't originate in Russian nor in English, but in Italian (it was used by Dante Alighieri in The Divine Comedy). From Italian it has entered many languages.
It is difficult to asses how frequently it is really used by searching corpora, because you can't filter out dictionaries of idioms (or at least I can't). But, the fact that it is found in dictionaries accounts for something: it is a proverb used in English.
Example of usage:
I have long been one of the most fervent supporters of the need of moral preparation among the population, a necessity which I feel more keenly than anyone else, especially more than those who hope to lower the effectiveness by aerial defense, or those who believe that after all the devil is not as black as he is painted.
From: The Command of the Air by Giulio Douhet, Joseph Patrick Harahan, Richard H. Kohn
(Yes, it is a translation from Italian, but it was published by University of Alabama, and if their editors didn't object, neither shall I).
To address the concern you raised in the comments: As it usually happens with proverbs, some are used more frequently than the others. Whether this one will work for you depends on the type of a research paper you are writing/translating, the specific area and the reason for which you chose an idiom as a title and in the end on your own personal preference. E.g. if it is a paper in nuclear physics it won't matter how often the proverb itself is used in English, because such titles are not frequent in the field at all; it will certainly grab the reader's attention. That being said, there is evidence that this is a proverb a native speaker of English would understand.